For a fun night out in Portland there is no better place than Bull Feeney's. Quality live music (multiple stages), great local beer, and lots of room make this a great place to take in the Portland nightlife. Friday's and Saturday's during the summer and St. Patrick's Day are the most popular nights at Bull Feeney's but almost any weekend night is bound to be fun.
The bar is a favorite with locals but is devoid of the pretentiousness and exclusion of many local favorites in other cities. Just show up and get ready for a good time.
The bar's location is also very central for the Old Port. So if you don't like what you find, go across the street and try something else out.
If you do stay the night don't try the same beer twice! They have a great variety of local beers and since they don't sell pitchers, there are no cost savings anyway.